1. Technical Field
Aspects and embodiments of the present invention are generally directed to inert materials and apparatus which simulate the look, feel, and/or X-ray response of explosive materials or devices such as improvised explosive devices (IEDs) or other potentially harmful devices. The inert materials and apparatus may be utilized for training of persons to identify actual harmful devices or testing X-ray devices and other instruments.
2. Discussion of Related Art
In numerous locations, most notably airports and other transportation hubs, packages, for example, passenger luggage may be screened for the presence of explosives, improvised explosive devices, or other potentially harmful devices. The screening process is often accomplished by the use of X-ray scanners. X-ray scanners may identify explosive materials by the density of the material and/or the effective atomic number (Zeff).
The two mechanisms primarily responsible for X-Ray attenuation at the energy levels typically utilized by explosive detection equipment are photoelectric absorption and Compton scattering. The photoelectric effect attenuates X-Ray transmission by absorption of incident X-Ray photons and resultant emission of a photoelectron and corresponding X-Ray. Compton scattering attenuates X-Ray transmission by inelastic scattering of incident X-Ray photons, resulting in a recoil electron and an emitted photon with lower energy. The attenuation of transmitted X-Rays is dominated by the photoelectric effect for elements with high atomic numbers whereas the attenuation by Compton scattering is dominant for elements with lower atomic numbers.
Compared to the photoelectric effect, the attenuation due to Compton scattering is relatively invariant with respect to incident X-Ray energy. Thus, detectors utilizing multi-energy X-Rays can distinguish materials of different atomic numbers based on the relative contributions of Compton scattering and photoelectric absorption on the overall absorption. Additional information about the density of the material may be inferred from the absorption of the high energy photons. In contrast with lower energy X-Rays, the absorption of high energy X-Rays are primarily due to Compton scattering which is roughly proportional to mass per cross sectional area. Algorithms may be put in place to automatically discriminate between materials which share characteristics (effective atomic number and density) with explosive materials and those that do not, thereby aiding in the detection. These X-ray scanners may sound an alarm or otherwise provide an indication of the suspected explosive material so that a trained agent may make a further investigation and respond accordingly. The X-ray scanners may identify different suspected explosive materials by different colors on a display.